Re: [f2fs-dev] [PATCH v3] f2fs: reduce expensive checkpoint trigger frequency

From: Chao Yu
Date: Mon Jun 24 2024 - 23:53:04 EST


On 2024/6/25 10:14, wangzijie wrote:
We may trigger high frequent checkpoint for below case:
1. mkdir /mnt/dir1; set dir1 encrypted
2. touch /mnt/file1; fsync /mnt/file1
3. mkdir /mnt/dir2; set dir2 encrypted
4. touch /mnt/file2; fsync /mnt/file2
...

Although, newly created dir and file are not related, due to
commit bbf156f7afa7 ("f2fs: fix lost xattrs of directories"), we will
trigger checkpoint whenever fsync() comes after a new encrypted dir
created.

In order to avoid such condition, let's record an entry including
directory's ino into global cache when we initialize encryption policy
in a checkpointed directory, and then only trigger checkpoint() when
target file's parent has non-persisted encryption policy, for the case
its parent is not checkpointed, need_do_checkpoint() has cover that
by verifying it with f2fs_is_checkpointed_node().

Reported-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
Tested-by: Zhiguo Niu <zhiguo.niu@xxxxxxxxxx>
Reported-by: Yunlei He <heyunlei@xxxxxxxxxxx>
Signed-off-by: Chao Yu <chao@xxxxxxxxxx>
---
v3:
- Recently, Zhiguo Niu reported the same issue, so I repost this
patch for comments.
fs/f2fs/f2fs.h | 2 ++
fs/f2fs/file.c | 3 +++
fs/f2fs/xattr.c | 16 ++++++++++++++--
include/trace/events/f2fs.h | 3 ++-
4 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index e2e0ca45f881..0094a8c85f4a 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -279,6 +279,7 @@ enum {
APPEND_INO, /* for append ino list */
UPDATE_INO, /* for update ino list */
TRANS_DIR_INO, /* for transactions dir ino list */
+ ENC_DIR_INO, /* for encrypted dir ino list */
FLUSH_INO, /* for multiple device flushing */
MAX_INO_ENTRY, /* max. list */
};
@@ -1147,6 +1148,7 @@ enum cp_reason_type {
CP_FASTBOOT_MODE,
CP_SPEC_LOG_NUM,
CP_RECOVER_DIR,
+ CP_ENC_DIR,
};
enum iostat_type {
diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 8198afb5fb9c..18b33b1f0c83 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -218,6 +218,9 @@ static inline enum cp_reason_type need_do_checkpoint(struct inode *inode)
f2fs_exist_written_data(sbi, F2FS_I(inode)->i_pino,
TRANS_DIR_INO))
cp_reason = CP_RECOVER_DIR;
+ else if (f2fs_exist_written_data(sbi, F2FS_I(inode)->i_pino,
+ ENC_DIR_INO))
+ cp_reason = CP_ENC_DIR;
return cp_reason;
}
diff --git a/fs/f2fs/xattr.c b/fs/f2fs/xattr.c
index f290fe9327c4..cbd1b88297fe 100644
--- a/fs/f2fs/xattr.c
+++ b/fs/f2fs/xattr.c
@@ -629,6 +629,7 @@ static int __f2fs_setxattr(struct inode *inode, int index,
const char *name, const void *value, size_t size,
struct page *ipage, int flags)
{
+ struct f2fs_sb_info *sbi = F2FS_I_SB(inode);
struct f2fs_xattr_entry *here, *last;
void *base_addr, *last_base_addr;
int found, newsize;
@@ -772,8 +773,19 @@ static int __f2fs_setxattr(struct inode *inode, int index,
if (index == F2FS_XATTR_INDEX_ENCRYPTION &&
!strcmp(name, F2FS_XATTR_NAME_ENCRYPTION_CONTEXT))
f2fs_set_encrypted_inode(inode);
- if (S_ISDIR(inode->i_mode))
- set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_CP);
+
+ if (S_ISDIR(inode->i_mode)) {
+ /*
+ * In restrict mode, fsync() always tries triggering checkpoint
+ * for all metadata consistency, in other mode, it only triggers
+ * checkpoint when parent's encryption metadata updates.
+ */
+ if (F2FS_OPTION(sbi).fsync_mode == FSYNC_MODE_STRICT)
+ set_sbi_flag(F2FS_I_SB(inode), SBI_NEED_CP);
+ else if (IS_ENCRYPTED(inode) &&
+ f2fs_is_checkpointed_node(sbi, inode->i_ino))
+ f2fs_add_ino_entry(sbi, inode->i_ino, ENC_DIR_INO);
+ }
same:
if (is_inode_flag_set(inode, FI_ACL_MODE)) {
diff --git a/include/trace/events/f2fs.h b/include/trace/events/f2fs.h
index 7ed0fc430dc6..48f2e399e184 100644
--- a/include/trace/events/f2fs.h
+++ b/include/trace/events/f2fs.h
@@ -139,7 +139,8 @@ TRACE_DEFINE_ENUM(EX_BLOCK_AGE);
{ CP_NODE_NEED_CP, "node needs cp" }, \
{ CP_FASTBOOT_MODE, "fastboot mode" }, \
{ CP_SPEC_LOG_NUM, "log type is 2" }, \
- { CP_RECOVER_DIR, "dir needs recovery" })
+ { CP_RECOVER_DIR, "dir needs recovery" }, \
+ { CP_ENC_DIR, "persist encryption policy" })
#define show_shutdown_mode(type) \
__print_symbolic(type, \
--
2.40.1

Hi, Chao
I noticed the discussion about patch v2, Jaegeuk mentioned no encryption case:
1) parent is checkpointed
2) set_xattr(dir) w/ new xnid
3) create(file)
4) fsync(file)
We will not trigger checkpoint() after this change.
So, how about adding a rule in need_do_checkpoint? We can judge if the parent has xnid
being checkpointed or not, if not we can still trigger checkpoint() and keep the same
behavior before this change.

Hi wangzijie,

It may cause performance overhead to get parent's xnid by parent ino,
so I prefer to tag ENC_DIR_INO for the inode if its parent's xnid is
not checkpointed, it that fine to you?

Thanks,




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